WASHINGTON — The Marine Corps' new heavy lift helicopter was officially approved for production this month, but reports indicate the overall acquisition cost has also increased by 7 percent.

The decision to move forward with production of the CH-53K King Stallion — called Milestone C in acquisition speak — was signed off on April 4 by an unnamed senior official currently performing the duties of the Under Secretary of Defense for Acquisition, Technology, and Logistics after performing a review of the program, according to a Marine Corps news release.

Weeks later, Bloomberg News reported that the Milestone C approval memo contained an Easter egg: a cost increase that brings the total value of the program from $29 billion to $32 billion. According to the memo obtained by Bloomberg, unit costs have also expanded to about $139 million per helicopter from just over $131 million.

A spokeswoman for Naval Air Systems Command, which oversees Marine Corps aircraft acquisitions, declined to comment on the report, which was based on information designated for "official use only." 

The publication of the memo could reignite congressional scrutiny of the program, which had already recently come under fire due to rumor of cost growth. In March, Rep. Niki Tsongas, D-Mass., said the unit costs had ballooned from $87.1 million to $122 million per helicopter — a figure even bigger than current estimates of the Air Force's F-35 model — leaving Marine Corps officials scrambling to put the cost of the helicopter in context.

Service officials maintained that the unit costs of the aircraft have not increased, but that the first few test articles are more expensive because of expenses occurred with standing up the production line and refining manufacturing processes. Once the program moves into full rate production, those costs should come down sharply, Marine Col. Henry Vanderborght, program manager for Marine Corps and Navy heavy lift helicopters, said at the Navy League’s annual Sea-Air-Space symposium.

The Pentagon typically does not include research and development when estimating unit costs, but Vanderborght acknowledged that, with both procurement and R&D factored in, the unit cost would average out to about $131 million per aircraft, although that price could be driven down by foreign sales.

Sikorsky Aircraft, now owned by Lockheed Martin, is set to deliver the first four CH-53Ks in 2018. The new cargo helicopters are designed to lift three times as much as its predecessor and have a cabin that is 12 inches wider, while also incurring lower operating costs, according to Sikorsky.

"The team has worked really hard to ensure we could get here, to Milestone C, and to begin low-rate initial production," Lt. Gen. Jon "Dog" Davis, the Marine Corps’ deputy commandant for aviation, stated in a news release earlier this month. "I'm very proud of all of them, and I'm looking forward to getting the most powerful heavy-lift helicopter ever designed into the hands of our Marines."

The service plans to buy 200 CH-53K to replace the CH-53E Super Stallion, and over the course of the program will transition eight active duty squadrons, one training squadron, and one reserve squadron from the E-model to the King Stallion. Two low rate initial production aircraft are under long lead procurement for parts and materials and will deliver in 2021, according to the Marine Corps.

Marine Corps Times reporter Jeff Schogol contributed to this report.